A.Ch. Bakarjiev, O.F. Makivchuk, V.A. Kriuchenko, A.V. Kuzmin, V.A. Anisimov Kirovgeology State Geological Enterprise, Kiev, Ukraine
Discovered commercial uranium deposits of Ukraine are presented in two genetic types: (a) endogenic metasomatic deposits in albitites of the Ukrainian shield and (b) exogenic epigenetic deposits in Paleogene sand-coal cover sediments of the Ukrainian shield. At present, deposits in albitites of the Kirovogradsky ore region are main source of uranium in Ukraine. They are being mined by underground method. Deposits in sand-coal sediments are not mined now due to ecological reasons. However, two of them (Devladovskoe and Bratskoe deposits) have been mined out in previous years using in situ leaching method.
In a whole, uranium mineral base of Ukraine according to uranium reserves can supply mining industry during several decades. At present, thirteen units of 5 nuclear power plants existing in Ukraine consume 2310 Mt of uranium annually. Uranium consumption will increase during following years in connection with installation of new reactors. In 2005 it will make 2890 Mt per year approximately. It is necessary to begin exploitation of new uranium deposits within Kirovogradsky ore region to provide such consumption. However, deposits discovered here are presented usually by low-grade ore with uranium content of 0.10–0.15% what specifies its cost.
These facts predestine significance of geological research in Ukraine to improve the quality of existing uranium mineral base. The examination of obtaining data about uranium mineralization in Ukraine including world experience in uranium geology shows that this problem can be solved in two main directions:
— To involve in exploitation sandstone uranium deposits, particularly deposits in coal-bearing sediments of the Ukrainian shield cover, suitable for in situ leaching,
— To discover commercial uranium deposits of new genetic types with high-grade (in comparison with deposits in albitites mining now) or complex uranium ore.
Advanced in situ leaching method using now in the world allows mining small low-grade deposits attaining high uranium recovery from ore (from 60% to 95% depending upon lithological ore type and ISL flowchart) and low mining cost (less than US$ 10–20 per kilogram of uranium).
Uranium deposits of sandstone type in Ukraine are located in Paleogene coal-bearing cover sediments of the Ukrainian shield fulfilling erosion tectonic paleodepressions in basement within the Dniprovsky brown coal basin (Dniprobas). Kirovgeology units have discovered and explored here seven small uranium deposits of this type (Devladovskoe, Bratskoe, Safonovskoe, Surskoe, Sadovoe, Novogurievskoe, and Chervonoyarskoe). As it was mentioned above, two of them (Devladovskoe and Bratskoe) have been mined out. These deposits are located in three uranium ore regions: (1) Saksagansko-Sursky, (2) Ingulo-Inguletsky, and (3) Yuzhno-Bugsky. Besides indicated deposits, a lot of uranium occurrences of the same type (more than 90) are discovered within these regions, but their assessment is not completed.
It should be noted that acid leaching was used only during exploitation of Devladovskoe and Bratskoe uranium deposits, as well as during experimental mining of some orebodies of
Safonovskoe, Sadovoe and Novogurievskoe deposits. The efficiency of other ISL technologies, particularly ecologically safe technology of carbonate-oxygen leaching was not studied at any mentioned deposit or occurrence. Attention should be paid also to the fact that complex character of mineralization on some deposits and occurrences of this type is established: except uranium ores contain such elements as molybdenum, selenium, thallium etc. However, their industrial importance practically is not certain.
To involve sandstone uranium deposits in operation the performance of the following works is planned:
(1) Complete development of Safonovskoe (43m), Sadovoe (25m) and Surskoe (7m) deposits for mining,
(2) Complete exploration of Novogurievskoe (39m) and Chervonoyarskoe (12m) deposits, carry out prospecting of Krinichanskoe (48m), Khristoforovskoe (15m), and Elenovskoe (47m) occurrences and evaluation of Khutorskoe (42m) and Petromihaylovskoe (8m) occurrences.
(3) Conduct complex of laboratory and field geo-technological tests on ISL sites within typical deposits using different ISL technologies with the objective to choose the main effective one according to uranium recovery and ecological requirements.
(4) Revise data about uranium mineralization at three ore regions of Dniprobas with the objective to outline areas within their limits for detail exploration at a scale 1:25 000 and most perspective occurrences that are subjects to a prime evaluation.
At present, according to the second point, systematization and generalization of a huge actual material about geological structure and uranium mineralization of Ukraine, which has collected for last 50 years is completed now. The analysis of this material has shown that there are serious geological preconditions to discover new uranium deposits in Ukraine which have high-grade ores in comparison with metasomatic deposits in albitites of Kirovogradsky ore region mining now. It is confirmed by detection of numerous uranium objects (occurrences and mineralization) of hydrothermal vein and vein-impregnated types in basement of the Ukrainian shield. The same objects characterized by increased uranium content (up to 1–3%) are revealed on a northwest slope of the shield, in a zone of upper Proterozoic structural-stratigraphic unconformity (unconformity-related type). However, the degree of radiometric investigation of the shield and its slopes is such that majority of uranium occurrences revealed here has not estimated for today.
It is caused by very difficult character of uranium mineralization of both types. In this connection executed researches are, as a rule, insufficient for the reasonable conclusion. The data on special deep research of investigating territory testify the same: within the limits of the Ukrainian shield only its insignificant part (about 35 000 km2 or 17.8% of its area) is covered by rather detailed deep exploration (1:50 000 scale and larger). Areas near slopes of a shield are investigated even worse.
In these conditions one of the important tasks of geological research is to clarify features of genesis and distribution of uranium formation of considered ore types: hydrothermal vein type on the shield and unconformity-related type on its northwest slope. Forecast criterion and research attributes of endogenic uranium formation with reference to geological conditions of the Ukrainian shield are established on the basis of analysis of actual data about uranium mineralization on the shield and its slopes. The most significant of them are thermal granite-gneiss domes generating uranium-bearing fluids, deep faults as channels of their moving to
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the upper horizons of the earth crust, and imposition of hydrothermal metasomatic process and uranium formation during different periods of tectono-magmatic activization in fault zones.
The map of high-grade Uranium mineralization of the Ukrainian shield of a scale 1:500 000 is made using indicated and other research criteria and attributes. As a result, 24 ore and potentially ore areas which are perspective to discover uranium deposits of hydro-thermal vein type and have general area of 18 570 km2 (or 9.3% of all territory of the shield) are allocated within its limits. Besides this, 2 potentially ore areas which are perspective to discover uranium deposits in a zone of upper Proterozoic structural-stratigraphic unconformity within Riphean Volyno-Orshansky paleodepression and have general area of 1970 km2 are also allocated on a northwest slope of the shield. Among them, 5 areas on the shield (Skvirsko-Tetievsky, Gayvoronsky, Kazankovsko-Zheltorechensky, Vasinovsky, and Volchansky) and one area on its northwest slope (northern part of Dubrovsky area) are allocated as the most favorable for detailed exploration. It was done according to the maximal combination of exploration attributes and the degrees of their development.
The majority of uranium occurrences, including Chervonoshahtarskoe occurrence (uranium contents 3.3% U on 1.85 m of its thickness), Severo-Bereznianskoe occurrence (uranium contents 0.47% on 15.85 m of its thickness including 5.65% on 0.85 m), and Vostochno-Annovskoe occurrence (uranium contents 1.20% on 6.67 m of its thickness including 2.34%
on 1.5 m) etc. is concentrated in the limits of indicated areas as well as within other perspective areas.
The further research within the limits of the allocated perspective areas and, first of all, within 6 prime areas consists in more profound study of available data about them as well as in the beginning of detailed exploration of a scale 1:25 000 – 1:10 000 on the defined separate local sites, and evaluation of the most perspective but not enough investigated occurrences.
According to all available data, the following occurrences are referred.
— Vostochno-Annovskoe (236p), Geikovskoe (131p) and Lagodovskoe (146p) within Kirovogradsky block,
— Sergeevskoe (245p) and Shirokobalkinskoe (235p) within Dniprovsky block,
— Dibrovskoe (221p), Guliaypolskoe (167p) and Barbasovskoe (47p) within Priazovsky block.
The practical realization of activities listed above during coming years in both directions will allow to decrease the cost of uranium mining in Ukraine and to improve the economy of uranium industry in the country.